Titanium Oxynitride Nanoparticles Anchored on Carbon Nanotubes as Energy Storage Materials

Scalable Synthesis of SiOx-TiON Composite As an Ultrastable Anode for Li-Ion Half/Full Batteries

Among various anode materials, SiOx is regarded as the next generation of promising anode due to its advantages of high theoretical capacity with 2680 mA h g-1, low lithium voltage platform, and rich natural resources. However, the pure SiOx-based materials have slow lithium storage kinetics attributed to their low electron/ion conductive properties and the large volume change during lithiation/delithiation, restricting their practical application. Optimizing the SiOx material structures and the fabricating methods to mitigate these fatal defects and adapt to the market demand for energy density is critical. Hence, SiOx material with TiO1-xNx phase modification has been prepared by simple, low-cost, and scalable ball milling and then combined with nitridation. Consequently, based on the TiO1-xNx modified layer, which boosts high ionic/electronic conductivity, chemical stability, and excellent mechanical properties, the SiOx@TON-10 electrode shows highly stable lithium-ion storage performance for lithium-ion half/full batteries due to a stable solid-electrolyte interface layer, fast Li+ transport channel, and alleviative volumetric expansion, further verifying its practical feasibility and universal applicability.

Engineering High-Performance SiOx Anode Materials with a Titanium Oxynitride Coating for Lithium-Ion Batteries

Micron-sized silicon oxide (SiOx) has been regarded as a promising anode material for new-generation lithium-ion batteries due to its high capacity and low cost. However, the distinct volume expansion during the repeated (de)lithiation process and poor conductivity can lead to structural collapse of the electrode and capacity fading. In this study, SiOx anode materials coated with TiO0.6N0.4 layers are fabricated by a facile solvothermal and thermal reduction technique. The TiO0.6N0.4 layers are homogeneously dispersed on SiOx particles and form an intimate contact. The TiO0.6N0.4 layers can enhance the conductivity and suppress volume expansion of the SiOx anode, which facilitate ion/electron transport and maintain the integrity of the overall electrode structure. The as-prepared SiOx-TiON-200 composites demonstrate a high reversible capacity of 854 mAh g-1 at 0.5 A g-1 with a mass loading of 2.0 mg cm-2 after 250 cycles. This surface modification technique could be extended to other anodes with low conductivity and large volume expansion for lithium-ion batteries.

Low-Temperature Synthesis of Titanium Oxynitride Nanoparticles

The synthesis of transition metal oxynitrides is complicated by extreme reaction conditions such as high temperatures and/or high pressures. Here, we show an unprecedented solution-based synthesis of narrowly dispersed titanium oxynitride nanoparticles of cubic shape and average size of 65 nm. Their synthesis is performed by using titanium tetrafluoride and lithium nitride as precursors alongside trioctylphosphine oxide (TOPO) and cetrimonium bromide (CTAB) as stabilizers at temperatures as low as 250 °C. The obtained nanoparticles are characterized in terms of their shape and optical properties, as well as their crystalline rock-salt structure, as confirmed by XRD and HRTEM analysis. We also determine the composition and nitrogen content of the synthesized particles using XPS and EELS. Finally, we investigate the applicability of our titanium oxynitride nanoparticles by compounding them into carbon fiber electrodes to showcase their applicability in energy storage devices. Electrodes with titanium oxynitride nanoparticles exhibit increased capacity compared to the pure carbon material.

Effect of the Morphology of the High-Surface-Area Support on the Performance of the Oxygen-Evolution Reaction for Iridium Nanoparticles

The development of affordable, low-iridium-loading, scalable, active, and stable catalysts for the oxygen-evolution reaction (OER) is a requirement for the commercialization of proton-exchange membrane water electrolyzers (PEMWEs). However, the synthesis of high-performance OER catalysts with minimal use of the rare and expensive element Ir is very challenging and requires the identification of electrically conductive and stable high-surface-area support materials. We developed a synthesis procedure for the production of large quantities of a nanocomposite powder containing titanium oxynitride (TiON x ) and Ir. The catalysts were synthesized with an anodic oxidation process followed by detachment, milling, thermal treatment, and the deposition of Ir nanoparticles. The anodization time was varied to grow three different types of nanotubular structures exhibiting different lengths and wall thicknesses and thus a variety of properties. A comparison of milled samples with different degrees of nanotubular clustering and morphology retention, but with identical chemical compositions and Ir nanoparticle size distributions and dispersions, revealed that the nanotubular support morphology is the determining factor governing the catalyst's OER activity and stability. Our study is supported by various state-of-the-art materials' characterization techniques, like X-ray photoelectron spectroscopy, scanning and transmission electron microscopies, X-ray powder diffraction and absorption spectroscopy, and electrochemical cyclic voltammetry. Anodic oxidation proved to be a very suitable way to produce high-surface-area powder-type catalysts as the produced material greatly outperformed the IrO2 benchmarks as well as the Ir-supported samples on morphologically different TiON x from previous studies. The highest activity was achieved for the sample prepared with 3 h of anodization, which had the most appropriate morphology for the effective removal of oxygen bubbles.

Heterostructured Titanium Oxynitride-Manganese Cobalt Oxide Nanorods as High-Performance Electrode Materials for Supercapacitor Devices

Metal oxynitrides have been considered recently as emerging electrode materials for supercapacitors. Herein, we converted titanate nanotubes into a series of titanium oxynitride (TiON) nanorods at nitridation temperatures of 800, 900, and 1000 °C in ammonia gas and tested them as supercapacitor electrodes. TiON-800, TiON-900, and TiON-1000 showed capacities of 60, 140, and 71 F g^-1, respectively, at a current density of 1 A g^-1. However, because of TiON's low capacity, a heterostructure (TiON-900/MnCo₂O₄) was designed based on the optimized TiON with MnCo₂O₄ (MCO). The heterostructure TiON-900-MCO and MCO electrode materials showed specific capacities of 515 and 381 F g^-1, respectively, at a current density of 1 A g^-1. The cycling stability retention of TiON-900 and MCO were 75 and 68%, respectively; moreover, the heterostructure of TiON-900-MCO reached 78% at a current density of 5 A g^-1 over 5000 cycles. The increased capacity and sustained cycling stability retention are attributable to the synergistic effect of TiON-900 and MCO. A coin cell (CC)-type symmetric supercapacitor prototype of TiON-900-MCO was fabricated and tested in the voltage range of 0.0-2.0 V in 1 M LiClO₄ in propylene carbonate/dimethyl carbonate electrolyte, and a 79% cycling retention capacity of TiON-900-MCO-CC was achieved over 10 000 cycles at a current density of 250 mA g^-1. We demonstrated a prototypical single cell of TiON-900-MCO-CC as a sustained energy output by powering a red-light emitting diode that indicated TiON-900-MCo electrode materials' potential application in commercial supercapacitor devices.

Improved Stability and Controllability in ZrN-Based Resistive Memory Device by Inserting TiO2 Layer

In this work, the enhanced resistive switching of ZrN-based resistive switching memory is demonstrated by embedding TiO2 layer between Ag top electrode and ZrN switching layer. The Ag/ZrN/n-Si device exhibits unstable resistive switching as a result of the uncontrollable Ag migration. Both unipolar and bipolar resistive switching with high RESET current were observed. Negative-SET behavior in the Ag/ZrN/n-Si device makes set-stuck, causing permanent resistive switching failure. On the other hand, the analogue switching in the Ag/TiO2/ZrN/n-Si device, which could be adopted for the multi-bit data storage applications, is obtained. The gradual switching in Ag/TiO2/ZrN/n-Si device is achieved, possibly due to the suppressed Ag diffusion caused by TiO2 inserting layer. The current-voltage (I-V) switching characteristics of Ag/ZrN/n-Si and Ag/TiO2/ZrN/n-Si devices can be well verified by pulse transient. Finally, we established that the Ag/TiO2/ZrN/n-Si device is suitable for neuromorphic application through a comparison study of conductance update. This paper paves the way for neuromorphic application in nitride-based memristor devices.

Mesoporous Titanium Oxynitride Monoliths from Block Copolymer-Directed Self-Assembly of Metal-Urea Additives

This report describes a simple one-pot soft-templating and ammonolysis-free approach to synthesize mesoporous crystalline titanium oxynitride by combining block copolymer-directed self-assembly with metal sol and urea precursors. The Pluronic F127 triblock copolymer was employed to structure-direct titanium-oxo-acetate sol nanoparticles and urea-formaldehyde into ordered hybrid mesostructured monoliths. The hybrid composites were directly converted into mesoporous crystalline titanium oxynitride and retained macroscale monolithic integrity up to 800 °C under nitrogen. Notably, the urea-formaldehyde additive provided nitrogen and rigid support to the inorganic mesostructure during crystallization. The resultant mesoporous titanium oxynitride exhibited good electrochemical catalytic activity toward hydrogen evolution reaction in 1 M KOH aqueous medium under applied bias. Our results suggest an inexpensive and safe pathway to generate ordered mesoporous crystalline metal oxynitride structures suitable for catalyst and energy-storage applications.

TiN Paper for Ultrafast-Charging Supercapacitors

Ultrafast-charging energy storage devices are attractive for powering personal electronics and electric vehicles. Most ultrafast-charging devices are made of carbonaceous materials such as chemically converted graphene and carbon nanotubes. Yet, their relatively low electrical conductivity may restrict their performance at ultrahigh charging rate. Here, we report the fabrication of a porous titanium nitride (TiN) paper as an alternative electrode material for ultrafast-charging devices. The TiN paper shows an excellent conductivity of 3.67 × 10⁴ S m^-1, which is considerably higher than most carbon-based electrodes. The paper-like structure also contains a combination of large pores between interconnected nanobelts and mesopores within the nanobelts. This unique electrode enables fast charging by simultaneously providing efficient ion diffusion and electron transport. The supercapacitors (SCs) made of TiN paper enable charging/discharging at an ultrahigh scan rate of 100 V s^-1 in a wide voltage window of 1.5 V in Na₂SO₄ neutral electrolyte. It has an outstanding response time with a characteristic time constant of 4 ms. Significantly, the TiN paper-based SCs also show zero capacitance loss after 200,000 cycles, which is much better than the stability performance reported for other metal nitride SCs. Furthermore, the device shows great promise in scalability. The filtration method enables good control of the thickness and mass loading of TiN electrodes and devices.

Enhanced shielding effectiveness in nanohybrids of graphene derivatives with Fe3O4 and ε-Fe3N in the X-band microwave region

Novel nanocomposites of reduced graphene oxide (rGO)-Fe3O4, denoted as 'rGO:IO, and nitrogen doped rGO-ε-Fe3N, denoted as 'NrGO:IN', were prepared by a modified polyol method, wherein both the reduction of graphene oxide and oxidation of Fe2+/Fe3+ ions occurred simultaneously, followed by ammonia nitridation. The electron microscopy analysis of the rGO:IO and NrGO:IN nanocomposites revealed unique morphologies. In rGO:IO, the Fe3O4 nanoparticles having a mean diameter of 38 nm were found to be uniformly anchored to the rGO sheet surface, whereas in NrGO:IN, the ε-Fe3N nanoparticles (∼150 nm) were shielded by the NrGO sheets. Superparamagnetic and weak ferromagnetic characteristics with saturation magnetization values of 39.5 and 46 emu g-1 were observed in the rGO:IO and NrGO:IN nanocomposites respectively, which can be attributed to the nature of the constituent magnetic nanoparticles, Fe3O4 and ε-Fe3N. In addition, the graphene derivatives such as rGO and NrGO contributed to the enhanced electrical properties of the nanocomposite. The electrochemical impedance spectroscopy analysis showed that, compared to pure Fe3O4 and ε-Fe3N nanoparticles, the total electrical resistance of rGO:IO and NrGO:IN was reduced by 33 344.8 and 1569.87 Ω cm-2, respectively, when combined with the rGO and NrGO sheets. Further, the electromagnetic shielding performance of the NrGO:IN nanocomposite was investigated for the first time and was compared with the other samples. Of the two prepared nanocomposites, NrGO:IN exhibited electromagnetic shielding effectiveness of 35.33 dB at 11.4 GHz, which is considerably larger than that of rGO:IO (14.4 dB at 8 GHz). This enhanced shielding effectiveness is not only due to the high inherent magnetic and electrical properties of ε-Fe3N nanoparticles, but also due to the 'particle shielded by sheet' morphology of the NrGO:IN, which enhances the charge accumulation at the heterogeneous interfaces of NrGO sheets/ε-Fe3N nanoparticles.

La0.8Sr0.2MnO3-Based Perovskite Nanoparticles with the A-Site Deficiency as High Performance Bifunctional Oxygen Catalyst in Alkaline Solution

Perovskite (La_0.8Sr_0.2)_1-xMn_1-xIr_xO₃ (x = 0 (LSM) and 0.05 (LSMI)) nanoparticles with particle size of 20-50 nm are prepared by the polymer-assisted chemical solution method and demonstrated as high performance bifunctional oxygen catalyst in alkaline solution. As compared with LSM, LSMI with the A-site deficiency and the B-site iridium (Ir)-doping has a larger lattice, lower valence state of transition metal, and weaker metal-OH bonding; therefore, it increases the concentration of oxygen vacancy and enhances both oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). LSMI exhibits superior ORR performance with only 30 mV onset potential difference from the commercial Pt/C catalyst and significant enhancement in electrocatalytic activity in the OER process, resulting in the best oxygen electrode material among all the reported perovskite oxides. LSMI also exhibits high durability for both ORR (only 18 mV negative shift for the half-wave potential compared with the initial ORR) and OER process with 10% decay. The electrochemical results indicate that the A-site deficiency and Ir-doping in perovskite oxides could be promising catalysts for the applications in fuel cells, metal-air batteries, and solar fuel synthesis.

The influence of surface area, porous structure, and surface state on the supercapacitor performance of titanium oxynitride: implications for a nanostructuring strategy

Underlying factors governing the capacitance and stability of titanium oxynitride are revealed.